Here you will find posts that are mostly about my work as an Oracle DBA. There may occasionally be other topics posted, but by and large this blog will be about Oracle and other geeky IT topics. Perl will likely be mentioned from time to time.

Wednesday, October 01, 2008

Undocumented functions in Oracle are always fun, and you just may find something useful.

The caveat of course is that they are undocumented. They can change without notice between releases or patch levels, so building apps that depend on them may be unwise.

They are often quite useful from a DBA perspective when used in SQL scripts.

Here are a few that I've played with. These are all found in Oracle 10.2.0.3

These functions have one thing in common - they have a prefix of SYS_OP_

Some of these appear to be identical to documented functions.

I don't know of any official explanation regarding the purpose of undocumented functions that seem to mimic documented functions. It could be that the source for the documented functions are separate from those that are documented, ensuring that functionality will not change for an undocumented function that is used in the Oracle kernel, even though its documented doppelganger may change in future releases.

In any case, undocumented functions are always interesting, and here are a few to play with.

Just keep in mind that these are undocumented, and as such may change or disappear entirely in future releases

sys_op_vacand - Return the binary AND of two raw values. Results are in hex

sys_op_vecbit - Return the value of the bit at position N in a raw value

The return value is 0 or 1

This is an interesting function as it can be used to determine the value of bits in a number. If for instance some flags are stored in a bit vector and you need to know the value of the 3 bit, this is an easy way to do it.